IBM offers peek at Cell, PS3

A bunch of new details on the Cell processor just have been released. Here are …

Sony, IBM, and Toshiba are set to fully unveil the details of the Cell processor at the upcoming International Solid State Circuits Conference (ISSCC) in early February. A few working papers submitted contain details of the Cell architecture and its interconnect technology, and both the EET and the Reg (among others) have fresh details gleaned from those papers. Here's a quick rundown for you:

Interestingly enough, published reports claim that Cell will use the POWER ISA, and not the PowerPC ISA. I'm not 100% sure what this signifies for the Cell, and I'd like to see readers' thoughts on why IBM picked POWER over the PPC subset. What do the differences between the two ISAs tell us about what we can expect from the Cell? Update: A reader in the know has clarified for me that IBM's marketing folks are now using "POWER architecture" as more of a catch-all for the entire family of POWER derivatives, and not just the original POWER ISA. So it doesn't necessarily mean anything that the news reports say "POWER-based" and now "PowerPC-based."

On a related note, I'm assuming for now that the Cell's SIMD units will use VMX/Altivec. But there's no news one way or the other on that matter.

According to the Reg, Cell sports some sort of virtualization features, where each core can run a different OS. When you combine this with the fact that Cell is also multithreaded, then Cell starts to look like POWER5 in some important respects. Nonetheless, I don't expect that Cell's microarchitecture will share much of anything with POWER5 or the 970.

Cell-based workstations are already in the hands of game developers. If you're reading this and you've got your hands on one and want to talk about it, email me at jstokes@arstechnica.com or pop into #mods on IRC. I mostly just want background for my reporting and writing on the topic and not "scoops" or "exclusives," since we at Ars don't traffic in that sort of thing. (In case you're suspicious, when was the last time you saw us tout "insider" info? We do indeed get such information, but we handle it differently than most.) At any rate, I don't expect anyone will contact me, but I figured I'd throw it out there since a lot of game developers read Ars.

All of the processing elements (a.k.a. Cells) are peers--even the ones on the network. I noted early on that this appeared to be the case, and this claim occasioned some controversy in the news discussion forum because network latencies would seem to prohibit any kind of network-based rendering in real time. We'll have to see what they do with this capability once the product hits the market.

Rambus designed the Cell's high-speed inter-element links. This makes me wonder if the PS3 will use Rambus DRAM, like the PS2. It's a great fit, and I wouldn't be surprised to see it happen.

There are a few more things I'm leaving out, but the above covers most of the new info released today.

On a parting note, the Reg speculates about Apple's possible uses for this chip. First off, Apple and Sony are competitors. This doesn't prohibit Apple from using the technology, but it's something to factor in when speculating in that direction. Second, should Apple find a use for the Cell I doubt seriously that it will be as the main CPU in some kind of workstation or rackmount rendering box. I'd expect the Cell to show up as a media coprocessor in an Apple machine. Steve Jobs has a history of putting dedicated DSP chips in his workstations; he did this back in the NeXT days, and it was speculated that we would do it with the G5 towers.